Apparatus for introducing coating metal to a vapor-deposition chamber



Feb. 4, 1969 J. MCKAY APPARATUS FOR INTRODUCING comma METAL TO A VAPOR-DEPOSITION CHAMBER Filed Feb. 2, 1966 INVEN TOR. JOSEPH M KA Y AI farney United States Patent 3,425,484 APPARATUS FOR INTRODUCING COATING METAL TO A VAPOR-DEPOSITION CHAMBER Joseph McKay, Whittier, Calif-2, assignor to United States Steel Corporation, a corporation of Delaware Filed Feb. 2, 1966, Ser. No. 524,535 US. Cl. 164--270 Int. Cl. B22d 11/10, 11/09; C23c 13/10 1 Claim ABSTRACT OF THE DISCLOSURE This invention relates to high-vacuum processes and, in particular, to a method and means for supplying coating metal to a crucible within a vacuum chamber wherein coating by vapor deposition is to be carried on.

The continuous coating of steel strip by the condensation of aluminum vapor thereon in a vacuum chamber has become commercially feasible. There is still a problem, however, in connection with the introduction into a crucible within the chamber, of the supply of make-up aluminum needed to permit continuous operation over substantial periods. One method is to feed aluminum wire through a sealed port in the wall of the vacuum chamber but there are obvious objections to such practice. It is accordingly the object of my invention to provide an improved method and apparatus for maintaining a continuous supply of make-up coating metal to the crucible through the wall of the vacuum chamber containing it.

In a preferred embodiment and practice of the invention, I mount a flow-through water-cooled tubular mold in the top of the vacuum chamber and pour molten metal continuously thereinto. The metal fills the mold, is cooled and solidifies therein, thus forming a tight plug which effectively seals the mold against the ingress of atmospheric gases to the chamber. Pinch rolls journaled in the chamber pull the solidified casting through the mold and lower it into a crucible where it is heated first to fusion and then further to vaporize it.

A complete understanding of the invention may be obtained from the following detailed description and explanation which refer to the accompanying drawing illustrating the present preferred embodiment. The drawing is a partial vertical section largely diagrammatic, through the vacuum chamber of a vapor-deposition coating apparatus having the invention incorporated therein.

Referring now in detail to the drawing, a vacuum chamber having a top wall 11 (and sides and bottom not identified by reference numeral) contains a crucible 12 adapted to contain molten aluminum to be vaporized when heated sufficiently by suitable means usually an electron-beam gun shown diagrammatically at G. Top wall 11 has an opening 13 therein through which extends a flow-through water-jacketed continuous-casting mold 14, preferably circular in section. The mold is mounted in the chamber by a collar 15 thereon, having a sealing ring 16, and secured to the margin of hole 13 by screws. The water jacket on the mold is designated 17. A substrate to be coated with aluminum from the crucible is indicated at S. Reference can be made to Simons Patent 3,425,484 Patented Feb. 4, 1969 "Ice No. 3,046,936 for a more detailed showing of an apparatus of this type.

A melting furnace or pouring ladle 18 is disposed above chamber 10 and has a bottom port or nozzle 19 to which mold 17 is coupled by a sealed joint 20. A plug 21 closes port 19 until it is desired to start the feeding of make-up coating metal to crucible 12. The plug may be placed and removed by a steel hook rod.

Aluminum ingots are melted in furnace 18 or elsewhere and the molten metal collected therein. At the beginning of operations, the mold 14 is plugged by a solid aluminum starter bar 22 backed up in the lower end thereof and held in place by pinch rolls 23. The pinch-roll shafts are journaled in suitable bearings and at least one extends through a sealed port in a side wall of chamber 10 so it may be driven from the outside.

On removal of plug 21 molten aluminum fills mold 14 and solidifies therein the freshly cast metal uniting with starter bar 22. Mold 14 being thus sealed, the pumps for evacuating chamber 10 are started and the pressure brought down to the customary low value. The electronbeam gun is then energized to melt any aluminum remaining in crucible 12 and, progressively, the lower end of bar 22. Pinch rolls 23 are then driven to lower the bar which is fused into the crucible and then succeeded by the following freshly cast bar which, after cooling to solidification, is likewise pulled through the mold by the pinch rolls. Shrinkage of the cast bar on cooling facilitates the extraction.

The descent of the bar east through mold 14 will be controlled according to the requirements of the crucible for make-up metal. For this purpose, a liquid-level controller 24 may be utilized to control operation of the pinch-roll motor.

When it becomes necessary to shut down operations, plug 21 is replaced. A solidified mass of aluminum may be left in the mold or it may be entirely extracted therefrom if replacement of the mold be necessary. In the former case, when starting up again, the upper end of the previously cast mass may be remelted in the mold by an electric resistance heating coil 25 disposed around the upper end thereof and about the port or nozzle 19, before fresh molten metal is teemed into the mold.

It will be evident from the foregoing that the invention provides a method and means for melting aluminum ingots outside the processing chamber and continuously feeding the necessary make-up metal through the wall thereof as a continuous casting which forms the closure and seal for the opening (mold) through which the metal is poured. The advantage of the invention is largely economic since ingot aluminum may be purchased at a saving over the cost of aluminum wire. A further advantage is that, by melting the metal outside the vacuum chamber, it is thoroughly degassed before entry thereinto, and impurities in the raw material float up to the surface so they can be manually removed. Finally, the make-up metal reaches the crucible at a temperature not far below the melting point and thus reduces the heating load on the electron-beam gun.

It should be noted that, while aluminum has been used as an example of coating metal to be vaporized, the

5 invention is applicable as well.to other metals.

ing metal, and means in said chamber for heating said crucible and melting and vaporizing coating metal, the combination therewith of an improved mechanism for supplying coating metal to said crucible, said mechanism comprising a vertical flow-through continuous-casting mold extending through said port and secured to said wall, a cooling jacket on said mold, means eirternal to said chamber for supplying liquid coating metal to said mold, and means in said chamber effective to pull downwardly into said crucible the continuous casting of coating metal formed and solidified in said mold.

References Cited UNITED STATES PATENTS 2,955,333 10/1960 Berry et al. 164252 2,959,829 11/1960 Brennan 16464 2,899,294 8/1959 Siemens 164-52 XR Eliot 164-64 Groteke et a1. 164338 XR Chambers 16464 Lane et a1 16452 X Lyman 16452 X Eng 11849 ClOugh et a1. 11849 FOREIGN PATENTS 2/1964 Austria. 11/ 1960 Great Britain.

J. SPENCER OVERHOLSER, Primary Examiner.

R. SPENCER ANNEAR, Assistant Examiner.

US. Cl. X.R. 

